1. The Search for Axion Dark Matter Pierre Sikivie U of Florida Fermilab Colloquium Nov. 15, 2006

2. Outline Introduction Axion cosmology Dark matter axion detection Solar axion detection Laser experiments

3. g A level pooltable on an inclined floor

4. The Strong CP Problem Because the strong interactions conserve P and CP,. The Standard Model does not provide a reason for to be so tiny, but a relatively small modification of the model does provide a reason …

5. g A self adjusting pooltable 1 ton

6. If a symmetry is assumed, relaxes to zero, and a light neutral pseudoscalar particle is predicted: the axion.

7. ff a a = 0.97 in KSVZ model 0.36 in DFSZ model

8. g A self adjusting pooltable 1 ton

9. g Searching for the pooltable oscillation quantum 1 ton

10. The invisible axion ? laboratory searches stellar evolution

11. g Relic pooltable oscillations 1 ton

12. The remaining axion window laboratory searches stellar evolution cosmology

13. Thermal axions q g a these processes imply an axion decoupling temperature thermal axion temperature today: = effective number of thermal degrees of freedom at axion decoupling

14. There are two axion populations: hot and cold. When the axion mass turns on, at QCD time,

15. Axion production by vacuum realignment V a V a initial misalignment angle

16. Axions are cold dark matter Density Velocity dispersion Effective temperature

17. g Searching for relic pooltable oscillations 1 ton

18. Axion dark matter is detectable a X A/D FFT

20. conversion power on resonance search rate for s/n = 4

21. ADMX Collaboration LLNL: S. Asztalos, C. Hagmann, D. Kinion, L.J Rosenberg, K. van Bibber, D. Yu U of Florida: L. Duffy, P. Sikivie, D. Tanner NRAO: R. Bradley

22. Axion Dark Matter eXperiment

23. High resolution analysis of the signal may reveal fine structure …

24. ADMX hardware high Q cavityexperimental insert

25. ADMX hemt amplifiers

26. ADMX MedRes limits

27. Upgrade with SQUID Amplifiers IBIB V o (t)  The basic SQUID amplifier is a flux- to-voltage transducer SQUID noise arises from Nyquist noise in shunt resistance scales linearly with T However, SQUIDs of conventional design are poor amplifiers above 100 MHz (parasitic couplings). Flux-bias to here

28. ADMX Upgrade: replace HEMTs (2 K) with SQUIDs (50 mK) In phase II of the upgrade, the experiment is cooled with a dilution refrigerator.

29. SQUIDs packaged into amplifiers Darin Kinion SQUIDs mounted on fridge

31. 4 cavity array – engineering run Piezo motors have low power dissipation, work at low temperatures and high magnetic fields

33. The cold dark matter particles lie on a 3-dimensional sheet in 6-dimensional phase space the physical density is the projection of the phase space sheet onto position space z z.

34. The cold dark matter particles lie on a 3-dimensional sheet in 6-dimensional phase space the physical density is the projection of the phase space sheet onto position space z z.

35. The cold dark matter particles lie on a 3-dimensional sheet in 6-dimensional phase space the physical density is the projection of the phase space sheet onto position space z z.

36. Phase space structure of spherically symmetric halos

37. Implications: 1.At every point in physical space, the distribution of velocities is discrete, each velocity corresponding to a particular flow at that location. 2. At some locations in physical space, where the number of flows changes, there is a caustic, i.e. the density of dark matter is very high there.

38. (from Binney and Tremaine’s book)

40. Galactic halos have inner caustics as well as outer caustics. If the initial velocity field is dominated by net overall rotation, the inner caustic is a “tricusp ring”.

41. simulations by Arvind Natarajan

42. The caustic ring cross-section an elliptic umbilic catastrophe D -4

45. On the basis of the self-similar infall model (Filmore and Goldreich, Bertschinger) with angular momentum (Tkachev, Wang + PS), the caustic rings were predicted to be in the galactic plane with radii was expected for the Milky Way halo from the effect of angular momentum on the inner rotation curve.

46. Composite rotation curve (W. Kinney and PS, astro-ph/9906049) combining data on 32 well measured extended external rotation curves scaled to our own galaxy

47. The Big Flow density velocity velocity dispersion previous estimates of the total local halo density range from 0.5 to 0.75 10 gr/cm -24 3 in the direction of galactic rotation in the direction away from the galactic center

48. an environmental peak, as seen in the medium and high resolution channels L. Duffy et al.

49. Axion to photon conversion in a magnetic field Theory P. S. ’83 L. Maiani, R. Petronzio and E. Zavattini ’86 K. van Bibber et al. ’87 G. Raffelt and L. Stodolsky, ‘88 K. van Bibber et al. ’89 Experiment D. Lazarus et al. ’92 R. Cameron et al. ‘93 S. Moriyama et al. ’98, Y. Inoue et al. ’02 K. Zioutas et al. 04 E. Zavattini et al. 05 a x with in vacuum probability

50. C ern A xion S olar T elescope Decommissioned LCH test magnet Rotating platform 3 X-ray detectors X-ray Focusing Device Sunset Photon detectors Sunset axions Sunrise axions Sunrise Photon detectors

53. Primakoff conversion of solar axions in crystals on Earth a x few keV Bragg scattering on crystal lattice Solax, Cosme ’98 Ge DAMA ‘01 NaI (100 kg)

54. Detecting solar axions using Earth’s magnetic field by H. Davoudiasl and P. Huber hep-ph/0509293 Sun Earth For axion masses, a low-Earth-orbit x-ray detector with an effective area of, pointed at the solar core, can probe down to, in one year.

55. Linearly polarized light in a constant magnetic field

56. Rotation

57. Rotation and Ellipticity

58. Experimental observation of optical rotation generated in vacuum by a magnetic field the average measured optical rotation is (3.9 0.5) 10 rad/pass through a 5 T, 1 m long magnet by E. Zavattini et al. (the PVLAS collaboration) Phys. Rev. Lett. 96 (2006) 110406 -12

59. PVLAS

60. The PVLAS result can be interpreted in terms of an axion-like particle b inconsistent with solar axion searches, stellar evolution descrepancy may be avoided in some models E. Masso and J. Redondo, hep-ph/0504202 I. Antoniadis, A. Boyarski and O. Ruchayskiy, hep-ph/0606306 R.N. Mohapatra and S. Nasri, hep-ph/0610068

61. Vacuum Phase I Phase II 4 He 3 He 2005 ~ 100 pressure settings 4 He (0 – 6mbar) 2006/7 ~ 700 for 3 He (6-60 mbar)

62. Shining light through walls K. van Bibber et al. ‘87 A. Ringwald ‘03 R. Rabadan, A. Ringwald and C. Sigurdson ‘05 P. Pugnat et al. 05 R. Battesti et al. A. Afanasev et al. x a x rate

63. Macroscopic forces mediated by axions Theory: J. Moody and F. Wilczek ’84 Experiment: A. Youdin et al. ’96 W.-T. Ni et al. ‘96 forces coupled to the f number density forces coupled to the f spin density background of magnetic forces

64. Conclusions Axions solve the strong CP problem and are a cold dark matter candidate. Axions haven’t been found yet. If axions exist, they are present on Earth as dark matter and emitted by the Sun. If an axion signal is found, it will provide a rich source of information on the structure of the Milky Way halo, and/or the Solar interior.

65. Telescope search for cosmic axions M.S. Bershady, M.T.Ressell and M.S. Turner ’90 galaxy clusters 3 – 8 eV B.D. Blout et al. ‘02 nearby dwarf galaxies 298 – 363 eV a